U.S. patent number 6,951,648 [Application Number 09/986,799] was granted by the patent office on 2005-10-04 for variant of lav viruses.
This patent grant is currently assigned to Institut Pasteur. Invention is credited to Marc Alizon, Luc Montagnier, Pierre Sonigo, Simon Wain-Hobson.
United States Patent |
6,951,648 |
Alizon , et al. |
October 4, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
Variant of LAV viruses
Abstract
A variant of a LAV virus, designated LAV.sub.ELI and capable of
causing AIDS. The cDNA and antigens of the LAV.sub.ELI virus can be
used for the diagnosis of AIDS and pre-AIDS.
Inventors: |
Alizon; Marc (Paris,
FR), Sonigo; Pierre (Paris, FR),
Wain-Hobson; Simon (Montigny les Bretonneux, FR),
Montagnier; Luc (Le Plessis Robinson, FR) |
Assignee: |
Institut Pasteur (Paris,
FR)
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Family
ID: |
21899340 |
Appl.
No.: |
09/986,799 |
Filed: |
November 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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423477 |
Apr 19, 1995 |
6337179 |
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656796 |
Feb 19, 1991 |
5869631 |
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038332 |
Apr 13, 1987 |
5034511 |
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Foreign Application Priority Data
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Jun 23, 1986 [EP] |
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86401380 |
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Current U.S.
Class: |
424/208.1;
424/188.1 |
Current CPC
Class: |
G01N
33/56988 (20130101); C07K 14/005 (20130101); C12N
2740/16021 (20130101); Y10S 530/826 (20130101); Y10S
435/975 (20130101); A61K 39/00 (20130101); Y10S
435/974 (20130101); C12N 2740/16022 (20130101) |
Current International
Class: |
C07K
14/005 (20060101); C07K 14/155 (20060101); C12Q
1/70 (20060101); A61K 39/21 (20060101); C12N
7/00 (20060101); C12N 7/01 (20060101); A61K
039/21 () |
Field of
Search: |
;424/184.1,185.1,188.1,193.1,195.1,208.1 ;514/2,12,15
;435/69.1,69.7 ;530/300,324-330 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Neurath et al., "Radioimmunoassay and Enzyme-Linked Immunoassay of
Antibodies Directed Against Lymphadenopathy-Associated Virus (LAV)
Proteins Larger Than the Core Protein (P24)," Journal of
Virological Methods, 12:85-92 (1985). .
Wain-Hobson et al., "Nucleotide Sequence of the AIDS Virus, LAV,"
Cell, 40:9-17 (1985). .
Wong-Staal et al., "Genomic Diversity of Human T-Lymphotropic Virus
Type III (HTLV-III), " Science, 229:759-762 (1985). .
Ellrodt et al., "Isolation of Human T-Lymphotropic Retrovirus (LAV)
from Zairian Married Couple, One with AIDS, One with Prodomes, "
The Lancet, 1383-1385 (1984). .
Ratner et al., "Complete Nucleotide Sequence of the AIDS Virus,
HTLV-III," Nature, 323:277-284 (1985). .
Sanchez-Pescador et al., "Nucleotide Sequence and Expression of an
AIDS-Associated Retrovirus (ARV-2)," Science, 227;484-492 (1985).
.
Muessing et al., "Nucleic Acid Structure and Expression of the
Human AIDS/Lymphadenopathy Retrovirus," Nature, 313:450-458 (1985).
.
Alizon et al., "Molecule Cloning of Lymphadenopathy-Associated
Virus," Nature, 312:757-760 (1984). .
Nature, 313, 277-284 (1985). .
Goodenow, et al., J. Acquir, Immune Defic. Syndr., 2:344-352
(1989). .
Gao et al., J. Virol., 68:7433-7447 (1994). .
Gallo et al., Nature (London) 333:564 (1988). .
Myers et al., Eds. Los Alamos Database in Human Retroviruses and
AIDS, Los Almos National Laboratory, Nwe Mexico, pp. IA1-IA3
(1990). .
Norrby et al., "Type-specific site-directed human immunodeficiency
virus serology," in Vaccines 88, Cold Spring Harbor Laboratory, pp.
335-339 (1988). .
Strongin, "Sensitivity, specificity, and predictive value of
diagnostic tests: definitions and clinical applications," in
Laboratory Diagnosis of Viral Infections, Lennette, ed., Marcel
Dekker, Inc., New York, pp. 211-219 (1992). .
Levy, Microbiol. Rev. 57:183-187, 211-213 (1993)..
|
Primary Examiner: Housel; James
Assistant Examiner: Parkin; Jeffrey S.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Parent Case Text
This is a continuation application Ser. No. 08/423,477. filed Apr.
19, 1995 now U.S. Pat. No. 6,337,179, which is a divisional
application of application Ser. No. 07/656,796, filed Feb. 19,
1991, now U.S. Pat. No. 5,869,631, which is a divisional
application of Ser. No. 07/038,332, filed Apr. 13, 1987, now U.S.
Pat. No. 5,034,511, which are incorporated herein by reference.
Claims
What is claimed is:
1. A polypeptide fragment, wherein said polypeptide fragment binds
to antibodies in LAS patient sera, and wherein said polypeptide
fragment comprises an HIV-1.sub.ELI epitope that does not react
with antibodies directed against specific epitopes of
HIV-1.sub.IIIB, HIV-1.sub.BRU, HIV-1.sub.ARV-2, or
HIV-1.sub.MAL.
2. The polypeptide fragment of claim 1, wherein said polypeptide
fragment comprises 5-150 amino acid residues.
3. An immunogenic composition comprising the polypeptide fragment
of claim 1.
4. An immunogenic composition comprising the polypeptide fragment
of claim 2.
5. A polypeptide fragment, wherein said polypeptide fragment binds
to antibodies in LAS patient sera, and wherein said polypeptide
fragment comprises an HIV-1.sub.ELI epitope that does not react
with antibodies directed against specific epitopes of
HIV-1.sub.IIIB, HIV-1.sub.BRU, HIV-1.sub.ARV-2.
6. The polypeptide fragment of claim 5, wherein said polypeptide
fragment comprises 5-150 amino acid residues.
7. An immunogenic composition comprising the polypeptide fragment
of claim 5.
8. An immunogenic composition comprising the polypeptide fragment
of claim 6.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a virus capable of inducing
lymphadenopathies (hereinafter "LAS") and acquired
immuno-depressive syndromes (hereinafter "AIDS"), to antigens of
this virus, particularly in a purified form, and to a process for
producing these antigens, particularly antigens of the envelope of
this virus. The invention also relates to polypeptides, whether
glycosylated or not, produced by the virus and to DNA sequences
which code for such polypeptides. The invention further relates to
cloned DNA sequences hybridizable to genomic RNA and DNA of the
lymphadenopathy associated virus (hereinafter "LAV") of this
invention and to processes for their preparation and their use. The
invention still further relates to a stable probe including a DNA
sequence which can be used for the detection of the LAV virus of
this invention or related viruses or DNA proviruses in any medium,
particularly biological, and in samples containing any of them.
An important genetic polymorphism has been recognized for the human
retrovirus which is the cause of AIDS and other diseases like LAS,
AIDS-related complex (hereinafter "ARC") and probably some
encephalopathies (for review, see Weiss, 1984). Indeed all of the
isolates, analyzed until now, have had distinct restriction maps,
even those recovered at the same place and time [Benn et al.,
1985]. Identical restriction maps have only been observed for the
first two isolates which were designated LAV [Alizon et al., 1984]
and human T-cell lymphotropic virus type 3 (hereinafter "HTLV-3")
[Hahn et al., 1984] and which appear to be exceptions. The genetic
polymorphism of the AIDS virus was better assessed after the
determination of the complete nucleotide sequence of LAV
[Wain-Hobson et al., 1985], HTLV-3[Ratner et al., 1985; Muesing et
al., 1985] and a third isolate designated AIDS-assoclated
retrovirus (hereinafter "ARV 2") [Sanchez-Pescador et al., 1985].
In particular, it appeared that, besides the nucleic acid
variations responsible for the restriction map polymorphism,
isolates could differ significantly at the protein level,
especially in the envelope (up to 13% of difference between ARV and
LAV), by both amino acids substitutions and reciprocal
insertions-deletions [Rabson and Martin, 1985].
Nevertheless, such differences did not go so far as to destroy the
immunological similarity of such isolates as evidenced by the
capabilities of their similar proteins, (e.g., core proteins of
similar nature, such as the p25 proteins, or similar envelope
glycoproteins, such as the 110-120 kD glycoproteins) to
immunologically cross-react. Accordingly, the proteins of any of
said LAV viruses can be used for the in vitro detection of
antibodies induced in vivo and present in biological fluids
obtained from individuals infected with the other LAV variants.
Therefore, these viruses are grouped together as a class of LAV
viruses (hereinafter "LAV-1 viruses").
SUMMARY OF THE INVENTION
In accordance with this invention, a new virus has been discovered
that is responsible for diseases clinically related to AIDS and
that can be classified as a LAV-1 virus but that differs
genetically from known LAV-1 viruses to a much larger extent than
the known LAV-1 viruses differ from each other. The new virus is
basically characterized by the cDNA sequence which is shown in
FIGS. 7A to 7I, and this new virus is hereinafter generally
referred to as "LAV.sub.ELI ".
Also in accordance with this invention, variants of the new virus
are provided. The RNAs of these variants and the related cDNAs
derived from said RNAs are hybridizable to corresponding parts of
the cDNA of LAV.sub.ELI. The DNA of the new virus also is provided,
as well as DNA fragments derived therefrom hybridizable with the
genomic RNA of LAV.sub.ELI, such DNA and DNA fragments particularly
consisting of the cDNA or cDNA fragments of LAV.sub.ELI or of
recombinant DNAs containing such cDNA or cDNA fragments.
DNA recombinants containing the DNA or DNA fragments of LAV.sub.ELI
or its variants are also provided. It is of course understood that
fragments which would include some deletions or mutations which
would not substantially alter their capability of also hybridizing
with the retroviral genome of LAV.sub.ELI are to be considered as
forming obvious equivalents of the DNA or DNA fragments referred to
hereinabove.
Cloned probes are further provided which can be made starting from
any DNA fragment according to the invention, as are recombinant
DNAs containing such fragments, particularly any plasmids
amplifiable in procaryotic or eucaryotic cells and carrying said
fragments. Using cloned DNA containing a DNA fragment of
LAV.sub.ELI as a molecular hybridization probe--either by marking
with radionucleotides or with fluorescent reagents--LAV virion RNA
may be detected directly, for example, in blood, body fluids and
blood products (e.g., in antihemophylic factors such as Factor VIII
concentrates). A suitable method for achieving such detection
comprises immobilizing LAVELI on a support (e.g., a nitrocellulose
filter), disrupting the virion and hybridizing with a labelled
(radiolabelled or "cold" fluorescent- or enzyme-labelled) probe.
Such an approach has already been developed for Hepatitis B virus
in peripheral blood (according to Scotto J. et al. Hepatology
(1983), 3, 379-384).
Probes according to the invention can also be used for rapid
screening of genomic DNA derived from the tissue of patients with
LAV related symptoms to see if the proviral DNA or RNA present in
their tissues is related to LAV.sub.ELI. A method which can be used
for such screening comprises the following steps: extraction of DNA
from tissue, restriction enzyme cleavage of said DNA,
electrophoresis of the fragments and Southern blotting of genomic
DNA from tissues and subsequent hybridization with labelled cloned
LAV provival DNA. Hybridization in situ can also be used. Lymphatic
fluids and tissues and other non-lymphatic tissues of humans,
primates and other mammalian species can also be screened to see if
other evolutionary related retroviruses exist. The methods referred
to hereinabove can be used, although hybridization and washings
would be done under non-stringent conditions.
The DNA according to the invention can be used also for achieving
the expression of LAV viral antigens for diagnostic purposes, as
well as for the production of a vaccine against LAV. Fragments of
particular advantage in that respect will be discussed later. The
methods which can be used are multifold: a) DNA can be transfected
into mammalian cells with appropriate selection markers by a
variety of techniques, such as calcium phosphate precipitation,
polyethylene glycol, protoplast-fusion, etc. b) DNA fragments
corresponding to genes can be cloned into expression vectors for E.
coli, yeast or mammalian cells and the resultant proteins purified.
c) The provival DNA can be "shot-gunned" (fragmented) into
procaryotic expression vectors to generate fusion polypeptides.
Recombinants, producing antigenically competent fusion proteins,
can be identified by simply screening the recombinants with
antibodies against LAV.sub.ELI antigens. Particular reference in
this respect is made to those portions of the genome of LAV.sub.ELI
which, in the figures, are shown to belong to open reading frames
and which encode the products having the polypeptidic backbones
shown.
Different polypeptides which appear in FIGS. 7A to 7I are still
further provided. Methods disclosed in European application 0 178
978 and in PCT application PCT/EP 85/00548, filed Oct. 18, 1985,
are applicable for the production of such peptides from
LAV.sub.ELI. In this regard, polypeptides are provided containing
sequences in common with polypeptides comprising antigenic
determinants included in the proteins encoded and expressed by the
LAV.sub.ELI genome. Means are also provided for the detection of
proteins of LAV.sub.ELI, particularly for the diagnosis of AIDS or
pre-AIDS or, to the contrary, for the detection of antibodies
against LAV.sub.ELI or its proteins, particularly in patients
afflicted with AIDS or pre-AIDS or more generally in asymtomatic
carriers and in blood-related products. Further provided are
immunogenic polypeptides and more particularly protective
polypeptides for use in the preparation of vaccine compositions
against AIDS or related syndroms.
Yet further provided are polypeptide fragments having lower
molecular weights and having peptide sequences or fragments in
common with those shown in FIGS. 7A to 7I. Fragments of smaller
sizes can be obtained by resorting to known techniques, for
instance, by cleaving the original larger polypeptide by enzymes
capable of cleaving it at specific sites. By way of examples may be
mentioned the enzyme of Staphylococcyus aureus V8,
.alpha.-chymotrypsine, "mouse sub-maxillary gland protease"
marketed by the Boehringer company, Vibrio alginolyticus chemovar
iophagus collagenase, which specifically recognizes the peptides
Gly-Pro, Gly-Ala, etc.
Other features of this invention will appear in the following
disclosure of data obtained starting from LAV.sub.ELI, in relation
to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B provide comparative restriction maps of the genomas
of LAV.sub.ELI as compared to LAV (Applicants' related new LAV
virus which is the subject of their copending application, filed
herewith) and LAV.sub.BRU (a known LAV isolate deposited at the
Collection Nationale des Cultures de Micro-organismes (hereinafter
"CNCM") of the Pasteur Institute, Paris, France under No. I-232 on
Jul. 15, 1983)
FIG. 2 shows comparative maps setting forth the relative positions
of the open reading frames of the above genomas;
FIGS. 3A-3F (also designated generally hereinafter "FIG. 3")
indicate the relative correspondance between the proteins (or
glycoproteins) encoded by the open reading frames, whereby amino
acid residues of protein sequences of LAV.sub.ELI are in vertical
alignment with corresponding amino acid residues (numbered) of
corresponding or homologous proteins or glycoproteins of
LAV.sub.BRU, as well as LAV.sub.MAL and ARV 2;
FIGS. 4A-4B (also designated generally hereinafter "FIG. 4")
provide tables quantitating the sequence divergence between
homologous proteins of LAV.sub.BRU, LAV.sub.ELI and LAV.sub.MAL
;
FIG. 5 shows diagrammatically the degree of divergence of the
different virus envelope proteins;
FIGS. 6A and 6B ("FIG. 6" when consulted together) render apparent
the direct repeats which appear in the proteins of the different
AIDS virus isolates.
FIGS. 7A-7I show the full nucleotidic sequences of LAV.sub.ELI.
DETAILED DESCRIPTION OF THE INVENTION
Characterization and Molecular Cloning of an African Isolate.
The different AIDS virus isolates concerned are designated by three
letters of the patients name, LAV.sub.BRU referring to the
prototype AIDS virus isolated in 1983 from a French homosexual
patient with LAS and thought to have been infected in the USA in
the preceding years [Barre-Sinoussi et al., 1983]. LAV.sub.ELI was
recovered in 1983 from a 24-year old woman with AIDS from Zaire.
Related LAV.sub.MAL was recovered in 1985 from a 7-year old boy
from Zaire. Recovery and purification of the LAV.sub.ELI virus were
performed according to the method disclosed in European Patent
Application 84 401834/138 667 filed on Sep. 9, 1984.
LAV.sub.ELI is indistinguishable from the previously characterized
isolates by its structural and biological properties in vitro.
Virus metabolic labelling and immune precipitation by patient ELI
sera, as well as reference sera, showed that the proteins of
LAV.sub.ELI had the same molecular weight (hereinafter "MW") as,
and cross-reacted immunologically with those of, prototype AIDS
virus (data not shown) of the LAV-1 class.
Reference is again made to European Application 178 978 and
International Application PCT/EP 85/00548 as concerns the
purification, mapping and sequencing procedures used herein. See
also the discussion under the headings "Experimental Procedures"
and "Significance of the Figures" hereinafter.
Primary restriction enzyme analysis of LAV.sub.ELI genome was done
by southern blot with total DNA derived from acutely infected
lymphocytes, using cloned LAV.sub.BRU complete genome as probe.
Overall cross-hybridization was observed under stringent
conditions, but the restriction profile of the Zairian isolate was
clearly different. Phage lambda clones carrying the complete viral
genetic information were obtained and further characterized by
restriction mapping and nucleotide sequence analysis. A Clone
(hereinafter "E-H12") was derived from LAV.sub.ELI infected cells
and contained an integrated provirus with 5' flanking cellular
sequences but a truncated 3' long terminal repeat (hereinafter
"LTR").
FIG. 1B gives a comparaison of the restriction maps derived from
the nucleotide sequences of LAV.sub.ELI, LAV.sub.MAL and prototype
LAV.sub.BRU, as well as from three other Zairian isolates
(hereinafter "Z1", "Z2", and "Z3" respectively) previously mapped
for seven restriction enzymes [Benn et al., 1985]. Despite this
limited number, all of the profiles are clearly different (out of
the 23 sites making up the map of LAV.sub.BRU, only seven are
present in all six maps presented), confirming the genetic
polymorphism of the AIDS virus. No obvious relationship is apparent
between the five Zairian maps, and all of their common sites are
also found in LAV.sub.BRU.
Conservation of the Genetic Organization.
The genetic organization of LAV.sub.ELI as deduced from the
complete nucleotide sequences of its cloned genome is identical to
that found in other isolates, i.e., 5'gag-pol-central
region-env-F3'. Most noticeable is the conservation of the "central
region" (FIG. 2), located between the pol and env genes, which is
composed of a series of overlapping open reading frames
(hereinafter "orf") previously designated Q, R, S, T, and U in the
ovine lentivirus visna [Sonigo et al., 1985]. The product of orf S
(also designated "tat") is implicated in the transactivation of
virus expression [Sodroski et al., 1985; Arya et al., 1985]; the
biological role of the product of orf Q (also designated "sor" or
"orf A") is still unknown [Lee et al., 1986; Kang et al., 1986]. Of
the three other orfs, R, T, and U, only orf R is likely to be a
seventh viral gene, for the following reasons the exact
conservation of its relative position with respect to Q and S (FIG.
2), the ponstant presence of a possible splice acceptor and of a
consensus AUG initiator codon, its similar codon usage with respect
to viral genes, and finally the fact that the variation of its
protein sequence within the different isolates is comparable to
that of gag, pol and Q (see FIG. 4).
Also conserved are the sizes of the U3, R and U5 elements of the
LTR (data not shown), the location and sequence of their regulatory
elements such as TATA box and AATAAA polyadenylation signal, and
their flanking sequences, i.e., primer binding site (hereinafter
"PBS") complementary to 3' end of tRNA.sup.LYS and polypurine tract
(hereinafter "PPT"). Most of the genetic variability within the LTR
is located in the 5' half of U3 (which encodes a part of orf F)
while the 3' end of U3 and R, which carry most of the cis-acting
regulatory elements, promoter, enhancer and trans-activating factor
receptor [Rosen et al., 1985], as well as the U5 element, are
well-conserved.
Overall, it clearly appears that this Zairian isolate, LAV.sub.ELI,
is the same type of retrovirus as the previously sequenced isolates
of American or European origin.
Variability of the Viral Proteins.
Despite their identical genetic organization, the LAV.sub.ELI and
LAV.sub.MAL shows substantial differences in the primary structure
of their proteins. The amino acid sequences of LAV.sub.ELI and
LAV.sub.MAL proteins are presented in FIGS. 3A-3F, aligned with
those of LAV.sub.BRU and ARV 2. Their divergence was quantified as
the percentage of amino acids substitutions in two-by-two
alignments (FIG. 4). The number of insertions and deletions that
had to be introduced in each of these alignments has also been
scored.
Three general observations can be made. First, the protein
sequences of the LAV.sub.ELI and LAV.sub.MAL are more divergent
from LAV.sub.BRU than are those of HTLV-3 and ARV 2 (FIG. 4A);
similar results are obtained if ARV 2 is taken as reference (not
shown). The range of genetic polymorphism between isolates of the
AIDS virus is considerably greater than previously observed.
Second, our two sequences confirm that the envelope is more
variable than the gag and pol genes. Here again, the relatively
small difference observed between the env of LAV.sub.BRU and HTLV-3
appears as an exception. Third, the mutual divergence of the
LAV.sub.ELI and LAV.sub.MAL (FIG. 4B) is comparable to that between
LAV.sub.BRU and either of them; as far as we can extrapolate from
only three sequenced isolates from the USA and Europe and two
(LAV.sub.ELI and LAV.sub.MAL) from Africa, this is indicative of a
wider evolution of the AIDS virus in Africa.
gag and pol: Their greater degree of conservation compared to the
envelope is consistent with their encoding important structural or
enzymatic activities. Of the three mature gag proteins, the p25
which was the first recognized immunogenic protein of LAV
[Barre-Sinoussi et al., 1983] is also the better conserved (FIG.
3). In gag and pol, differences between isolates are principally
due to point mutations, and only a small number of insertional or
deletional events is observed. Among these, we must note the
presence in the overlapping part of gag and pol of LAV.sub.BRU of
an insertion of 12 amino acids (AA) which is encoded by the second
copy of a 36 bp direct repeat present only in this isolate and in
HTLV-3. This duplication was omitted because of a computing error
in the published sequence of LAV.sub.BRU (position 1712,
Wain-Hobson et al., 1985) but was indeed present in the HTLV-3
sequences [Ratner et al., 1985 Muesing et al., 1985].
env: Three segments can be distinguished in the envelope
glycoprotein precursor [Allan et al., 1985 Montagnier et al., 1985;
DiMarzoVeronese et al., 1985]. The first is the signal peptide
(positions 1-33 in FIG. 3), and its sequence appears as variable;
the second segment (pos. 34-530) forms the outer membrane protein
(hereinafter "OMP" or "gp110") and carries most of the genetic
variations, and in particular almost all of the numerous reciprocal
insertions and deletions; the third segment (531-877) is separated
from the OMP by a potential cleavage site following a constant
basic stretch (Arg-Glu-Lys-Arg) and forms the transmembrane protein
(hereinafter "TMP" or "gp 41") responsible for the anchorage of the
envelope glycoprotein in the cellular membrane. A better
conservation of the TMP than the OMP has also been observed between
the different murine leukemia viruses (hereinafter "MLV") [Koch et
al., 1983] and could be due to structural constraints.
From the alignment of FIG. 3 and the graphical representation of
the envelope variability shown in FIG. 5, we clearly see the
existence of conserved domains, with little or no genetic
variation, and hypervariable domains, in which even the alignment
of the different sequences is very difficult, because of the
existence of a large number of mutations and of reciprocal
insertions and deletions. We have not included the sequence of the
envelope of the HTLV-3 isolate since it so close to that of
LAV.sub.BRU (cf. FIG. 4), even in the hypervariable domains, that
it did not add anything to the analysis. While this graphical
representation will be refined by more sequence data, the general
profile is already apparent, with three hypervariable domains (Hy1,
2 and 3) all being located in the OMP and separated by three
well-conserved stretches (residues 37-130, 211-289, and 488-530 of
FIG. 3 alignment) probably associated with important biological
functions.
In spite of the extreme genetic variability, the folding pattern of
the envelope glycoprotein is probably constant. Indeed the position
of virtually all of the cysteine residues is conserved within the
different isolates (FIGS. 3 and 5), and the only three variable
cysteines fall either in the signal peptide or in the very
C-terminal part of the TMP. The hypervariable domains of the OMP
are bounded by conserved cysteines, suggesting that they may
represent loops attached to the common folding pattern. Also the
calculated hydropathic profiles [Kyte and Doolittle, 1982] of the
different envelope proteins are remarkably conserved (not
shown).
About half of the potential N-glycosylation sites, Asn-X-Ser/Thr,
found in the envelopes of the Zairian isolates map to the same
positions in LAV.sub.BRU (17/26 for LAV.sub.ELI and 17/28 for
LAV.sub.MAL). The other sites appear to fall within variable
domains of env, suggesting the existence of differences in the
extent of envelope glycosylation between different isolates.
Other viral proteins: Of the three other identified viral proteins,
the p27 encoded by orf F, 3' of env [Allan et al., 1985b] is the
most variable (FIG. 4). The proteins encoded by orfs Q and S of the
central region are remarkable by their absence of
insertions/deletions. Surprisingly, a high frequency of amino acids
substitutions, comparable to that observed in env, is found for the
product of orf S (trans-activating factor). On the other hand, the
protein encoded by orf Q is no more variable than gag. Also
noticeable is the lower variation of the proteins encoded by the
central regions of LAV.sub.ELI and LAV.sub.MAL.
With the availability of the complete nucleotide sequence from five
independant isolates, some general features of the AIDS virus'
genetic variability are now emerging. Firstly, its principal cause
is point mutations which very often result in amino acid
substitutions and which are more frequent in the 3' part of the
genome (orf S, env and orf F). Like all RNA viruses, the
retroviruses are thought to be highly subject to mutations caused
by errors of the RNA polymerases during their replication, since
there is no proofreading, of this step [Holland et al., 1982;
Steinhauer and Holland, 1986].
Another source of genetic diversity is insertions/deletions. From
the FIG. 3 alignments, insertional events seem to be implicated in
most of the cases, since otherwise deletions should have occurred
in independant isolates at precisely the same locations.
Furthermore, upon analyzing these insertions, we have observed that
they most often represent one of the two copies of a direct repeat
(FIG. 6). Some are perfectly conserved like the 36 bp repeat in the
gag-pol overlap of LAV.sub.BRU (FIG. 6a); others carry point
mutations resulting in amino acid substitutions, and as a
consequence, they are more difficult to observe, though clearly
present, in the hypervariable domains of env. As noted for point
mutations, env gene and orf F also appear as more susceptible to
that form of genetic variation than the rest of the genome. The
degree of conservation of these repeats must be related to their
date of occurrence in the analyzed sequences: the more degenerated,
the more ancient. A very recent divergence of LAV.sub.BRU and
HTLV-3 is suggested by the extremely low number of mismatched AA
between their homologous proteins. However, one of the LAV.sub.BRU
repeats (located in the Hy1 domain of env) is not present in
HTLV-3, indicating that this generation of tandem repeats is a
rapid source of genetic diversity. We have found no traces of such
a phenomenon, even when comparing very closely related viruses,
such as the Mason-Pfizer monkey virus (hereinafter "MPMV") [Sonigo
et al., 1986], and an immunosuppressive simian virus (hereinafter
"SRV-1") [Power et al., 1986]. Insertion or deletion of one copy of
a direct repeat have been occasionally reported in mutant
retroviruses [Shimotohno and Temin, 1981; Darlix, 1986], but the
extent to which we observe this phenomenon is unprecedented. The
molecular basis of these duplications is unclear, but could be the
"copy-choice" phenomenon, resulting from the diploidy of the
retroviral genome [Varmus and Swanstrom, 1984; Clark and Mak,
1983]. During the synthesis of the first-strand of the viral DNA,
jumps are known to occur from one RNA molecule to another,
especially when a break or a stable secondary structure is present
on the template; an inaccurate re-initiation on the other RNA
template could result in the generation (or the elimination) of a
short direct repeat.
Genetic variability and subsequent antigenic modifications have
often been developed by micro-organisms as a means for avoiding the
host's immune response, either by modifying their epitopes during
the course of the infection, as in trypanosomes [Borst and Cross,
1982], or by generating a large repertoire of antigens, as observed
in influenza virus [Webster et al., 1982]. As the human AIDS virus
is related to animal lentiviruses [Sonigo et al., 1985; Chiu et
al., 1985], its genetic variability could be a source of antigenic
variation, as can be observed during the course of the infection by
the ovine lentivirus visna [Scott et al., 1979; Clements et al.,
1980] or by the equine infectious anemia virus (hereinafter "EIAV")
[Montelaro et al., 1984]. However, a major discrepancy with these
animal models is the extremely low, and possibly nonexistent,
neutralizing activity of the sera of individuals infected by the
AIDS virus, whether they are healthy carriers, displaying minor
symptoms, or afflicted with AIDS [Weiss et al., 1985; Clavel et
al., 1985]. Furthermore, even for the visna virus the exact role of
antigenic variation in the pathogenesis is unclear [Thormar et al.,
1983; Lutley et al., 1983]. We rather believe that genetic
variation represents a general selective advantage for lentiviruses
by allowing an adaptation to different environments, for example by
modifying their tissue or host tropisms. In the particular case of
the AIDS virus, rapid genetic variations are tolerated, especially
in the envelope. This could allow the virus to become adapted to
different "micro-environments" of the membrane of their principal
target cells, namely the T4 lymphocytes. These "micro-environments"
could result from the immediate vicinity of the virus receptor to
polymorphic surface proteins, differing either between individuals
or between clones of lymphocytes.
Conserved Domains in the AIDS Virus Envelope
Since the proteins of most of the isolates are antigenically
cross-reactive, the genotypic differences do not seem to affect the
sensitivity of actual diagnostic tests, based upon the detection of
antibodies to the AIDS virus and using purified virions as
antigens. They nevertheless have to be considered for the
development of the "second-generation" tests, that are expected to
be more specific, and will use smaller synthetic or
genetically-engineered viral antigens. The identification of
conserved domains in the highly immunogenic envelope glycoprotein
and the core structural proteins (gag) is very important for these
tests. The conserved stretch found at the end of the OMP and the
beginning of the TMP (490-620, FIG. 3) could be a good candidate,
since a bacterial fusion protein containing this domain was
well-detected by AIDS patients' sera [Chang et al., 1985].
The envelope, specifically the OMP, mediates the interaction
between a retrovirus and its specific cellular receptor [DeLarco
and Todaro, 1976; Robinson et al., 1980]. In the case of the AIDS
virus, in vitro binding assays have shown the interaction of the
envelope glycoprotein gp110 with the T4 cellular surface antigen
[McDougal et al., 1986], already thought to be closely associated
with the virus receptor [Klatzmann et al., 1984; Dagleish et al.,
1984]. Identification of the AIDS virus envelope domains that are
responsible for this interaction (receptor-binding domains) appears
to be fundamental for understanding of the host-viral interactions
and for designing a protective vaccine, since an immune response
against these epitopes could possibly elicit neutralizing
antibodies. As the AIDS virus receptor is at least partly formed of
a constant structure, the T4 antigen, the binding site of the
envelope is unlikely to be exclusively encoded by domains
undergoing drastic genetic changes between isolates, even if these
could be implicated in some kind of an "adaptation". One or several
of the conserved domains of the OMP (residues 37-130, 211-289, and
488-530 of FIG. 3 alignment), brought together by the folding of
the protein, must play a part in the virus-receptor interaction,
and this can be explored with synthetic or genetically-engineered
peptides derived from these domains, either by direct binding
assays or indirectly by assaying the neutralizing activity of
specific antibodies raised against them.
African AIDS Viruses
Zaire and the neighboring countries of Central Africa are
considered as an area endemic with the AIDS virus infection, and
the possibility that the virus has emerged in Africa has became a
subject of intense controversy (see Norman, 1985). From the present
study, it is clear that the genetic organization of Zairian
isolates is the same as that of american isolates, thereby
indicating a common origin. The very important sequence differences
observed between the proteins are consistent with a divergent
evolutionary process. In addition, the two African isolates are
mutually more divergent than the American isolates already
analyzed; as far as that observation can be extrapolated, it
suggests a longer evolution of the virus in Africa and is also
consistent with the fact that a larger fraction of the population
is exposed than in developed countries.
A novel human retrovirus with morphology and biologocal properties
(cytopathogenicity, T4 tropism) similar to those of LAV, but
nevertheless clearly genetically and antigenically distinct from
it, was recently isolated from two patients with AIDS originating
from Guinea Bissau, West-Africa [Clavel et al., 1986]. In
neighboring Senegal, the population was seemingly exposed to a
retrovlrus also distinct from LAV but apparently non-pathogenic
[Barin et al., 1985; Kanki et al., 1986]. Both of these novel
African retro-viruses seem to be antigenically related to the
simian T-cell lymphotropic virus (hereinafter "STLV-III") shown to
be widely present in healthy African green monkeys and other simian
species [Kanki et al. 1985]. This raises the possibility of a large
group of African primate lentiviruses, ranging from the apparently
non-pathogenic simian viruses to the LAV-type viruses. Their
precise relationship will only be known after their complete
genetic characterization, but it is already very likely that they
have evolved from a common progenitor. The important genetic
variability we have observed between isolates of the AIDS virus in
Central Africa is probably a hallmark of this entire group and may
account for the apparently important genetic divergence between its
members (loss of cross-antigenicity in the envelopes). In this
sense, the conservation of the tropism for the T4 lymphocytes
suggests that it is a major advantage aquired by these
retroviruses.
Experimental Procedures
Virus Isolation
LAV.sub.ELI was isolated from the peripheral blood lymphocytes of
the patient as described [Barre-Sinoussi et al., 1983]. Briefly,
the lymphocytes were fractionated and co-cultivated with
phytohaemagglutinin-stimulated normal human lymphocytes in the
presence of interleukin 2 and anti-alpha interferon serum. Viral
production was assessed by cell-free reverse transcriptase
(hereinafter "RT") activity assay in the cultures and by electron
microscopy.
Molecular Cloning
Normal donor lymphocytes were acutely infected (10.sup.4 cpm of RT
activity/10.sup.6 cells) as described [Barre-Sinoussi et al.,
1983], and total DNA was extracted at the beginning of the RT
activity peak. A lambda library using the L47-1 vector [Loenen and
Brammar, 1982] was constructed by partial HindIII digestion of the
DNA as already described [Alizon et al., 1984]. About 5.10.sup.5
plaques for LAV.sub.ELI, obtained by in vitro packaging (Amersham),
were plated on E. coli LA101 and screened in situ under stringent
conditions, using the 9 kb SacI insert of the clone lambda J19
[Alizon et al., 1984] carrying most of the LAV.sub.BRU genome as
probe. Clones displaying positive signals were plaque-purified and
propagated on E. coli C600 recBC, and the recombinant phage E-H12
carrying the complete genetic information of LAV.sub.ELI was
further characterized by restriction mapping.
Nucleotide Sequence Strategy
Viral fragments derived from E-H12 were sequenced by the dideoxy
chain terminator procedure [Sanger et al., 1977] after "shotgun"
cloning in the M13 mp8 vector [Messing and Viera, 1982] as
previously described [Sonigo et al., 1985]. The viral genome of
LAV.sub.ELI is 9176 nucleotides long as shown in FIGS. 7A-7I. Each
nucleotide of LAV.sub.ELI was determined from more than 5
independent clones on average.
Significance of the Figures
FIG. 1 contains an analysis of AIDS virus isolates, showing:
A/ Restriction maps of the inserts of phage lambda clones derived
from cells infected with LAV.sub.ELI (E-H12) and with LAV.sub.MAL
(hereinfter "M-H11"). The schematic genetic organization of the
AIDS virus has been drawn above the maps. The LTRs are indicated by
solid boxes. Restriction sites are indicated as follows: A:Aval;
B:BamHI; Bg:BgIII; E:EcoRI; H:HindIII; Hc:HincII; K:KpnI; N:NdeI;
P:PstI; S:SacI; and X:XbaI.
Asterisks indicate the HindIII cloning sites in lambda L47-1
vector.
B/ A comparison of the sites for seven restriction enzymes in six
isolates the prototype AIDS virus LAV.sub.BRU, LAV.sub.MAL and
LAV.sub.ELI ; and Z1, Z2 and Z3. Restriction sites are represented
by the following symbols vertically aligned wih the symbols in FIG.
1a: .circle-solid.: BgIII; .star-solid.:EcoRI; .gradient.:HincII;
.tangle-soliddn.:HindIII; .diamond-solid.:KpnI; .diamond.:NdeI; and
o:SacI.
FIG. 2 shows the genetic organization of the central region in AIDS
virus isolates. Stop codons in each phase are represented as
vertical bars. Vertical arrows indicate possible AUG initiation
codons. Splice acceptor (A) and donor (D) sites identified in
subgenomic viral mRNA [Muesing et al., 1985] are shown below the
graphic of LAV.sub.BRU and corresponding sites in LAV.sub.ELI and
LAV.sub.MAL are indicated. PPT indicates the repeat of the
polypurine tract flanking the 3'LTR. As observed in LAV.sub.BRU
[Wain-Hobson et al., 1985], the PPT is repeated 256 nucleotides 5'
to the end of the pol gene in both the LAV.sub.ELI and LAV.sub.MAL
sequences, but this repeat is degenerated at two positions in
LAV.sub.ELI.
FIG. 3 shows an alignment of the protein sequences of four AIDS
virus isolates. Isolate LAV.sub.BRU [Wain-Hobson et al., 1985] is
taken as reference; only differences with LAV.sub.BRU are noted for
ARV 2 [Sanchez-Pescador et al., 1985] and the two Zairian isolates
LAV.sub.MAL and LAV.sub.ELI. A minimal number of gaps (-) were
introduced in the alignments. The NH.sub.2 -termini of p25.sup.gag
and p18.sup.gag are indicated [Sanchez-Pescador, 1985]. The
potential cleavage sites in the envelope precursor [Allan et al.,
1985a; diMarzoVeronese, 1985] separating the signal peptide
(hereinafter "SP"), OMP and TMP are indicated as vertical arrows;
conserved cysteines are indicated by black circles and variable
cysteines are boxed. The one letter code for each amino acid is as
follows: A:Ala; C:Cys; D:Asp; E:Glu; F:Phe; G:Gly; H:His; I:Ile;
K:Lys; L:Leu; M:Met; N:Asn; P:Pro; Q:Gln; R:Arg; S:Ser; T:Thr;
V:Val; W:Trp; Y:Tyr.
FIG. 4 shows a quantitation of the sequence divergence between
homologous proteins of different isolates. Part A of each table
gives results deduced from two-by-two alignments using the proteins
of LAV.sub.BRU as reference, part B, those of LAV.sub.ELI as
reference. Sources: Muesing et al., 1985 for HTLV-3;
Sanchez-Pescador et al., 1985 for ARV 2 and Wain-Hobson et al.,
1985 for LAV.sub.BRU. For each case in the tables, the size in
amino acids of the protein (calculated from the first methionine
residue or from the beginning of the orf for pol) is given at the
upper left part. Below are given the number of deletions (left) and
insertions (right) necessary for the alignment. The large numbers
in bold face represent the percentage of amino acids substitutions
(insertions/deletions being excluded). Two by two alignments were
done with computer assistance [Wilburg and Lipman, 1983], using a
gag penalty of 1, K-tuple of 1, and window of 20, except for the
hypervariable domains of env, where the number of gaps was made
minimum, and which are essentially aligned as shown in FIG. 3. The
sequence of the predicted protein encoded by orf R of HTLV-3 has
not been compared because of a premature termination relative to
all other isolates.
FIG. 5 shows the variability of the AIDS virus envelope protein.
For each position x of the alignment of env (FIG. 3), variability
V(x) was calculated as: V(x)=number of different amino-acids at
position x/frequency of the most abundant amino acid at position x.
Gaps in the alignments are considered as another amino acid. For an
alignment of 4 proteins, V(x) ranges from 1 (identical AA in the 4
sequences) to 16 (4 different AA). This type of representation has
previously been used in a compilation of the AA sequence of
immunoglobulins variable regions [Wu and Kabat, 1970]. Vertical
arrows indicate the cleavage sites; asterisks represent potential
N-glysosylation sites (N-X-S/T) conserved in all four isolates;
black triangles represent conserved cysteine residues. Black
lozanges mark the three major hydrophobic domains: OMP, TMP and SP;
and the hyper-variable domains: Hy1, 2 and 3.
FIG. 6 shows the direct repeats in the proteins of different AIDS
virus isolates. These examples are derived from the aligned
sequences of gag (a, b), F (c,d) and env (e, f, g, h) shown in FIG.
3. The two elements of the direct repeat are boxed, while
degenerated positions are underlined.
FIGS. 7A-7I show the complete cDNA sequence of LAV.sub.ELI of this
invention.
The invention thus pertains more specifically to the proteins,
glycoproteins and other polypeptides including the polypeptidic
structures shown in the FIGS. 1-7. The first and last amino acid
residues of these proteins, glycoproteins and polypeptides carry
numbers computed from a first amino acid of the open-reading frames
concerned, although these numbers do not correspond exactly to
those of the LAV.sub.ELI proteins concerned, rather to the
corresponding proteins of the LAVBRU or sequences shown in FIGS.
3A, 3B and 3C. Thus a number corresponding to a "first amino acid
residue" of a LAV.sub.ELI protein corresponds to the number of the
first amino-acyl residue of the corresponding LAV.sub.BRU protein
which, in any of FIGS. 3A, 3B or 3C, is in direct alignment with
the corresponding first amino acid of the LAV.sub.ELI protein. Thus
the sequences concerned can be read from FIGS. 7A-7I to the extent
where they do not appear with sufficient clarity from FIGS.
3A-3F.
The preferred protein sequences of this invention extend between
the corresponding "first" and "last" amino acid residues. Also
preferred are the protein(s)- or glycoprotein(s)-portions including
part of the sequences which follow:
OMP or gp110 proteins, including precursors:
1 to 530
OMP or gp110 without precursor:
34-530
Sequence carrying the TMP or gp41 protein:
531-877, particularly
680-700
well conserved stretches of OMP:
37-130,
211-289 and
488-530
well conserved stretch found at the end of the OMP and the
beginning of TMP:
490-620.
Proteins containing or consisting of the "well conserved stretches"
are of particular interest for the production of immunogenic
compositions and (preferably in relation to the stretches of the
env protein) of vaccine compositions against the LAV-1 viruses.
The invention concerns more particularly all the DNA fragments
which have been more specifically referred to in the drawings and
which correspond to open reading frames. It will be understood that
one skilled in the art will be able to obtain them all, for
instance by cleaving an entire DNA corresponding to the complete
genome of LAV.sub.ELI such as by cleavage by a partial or complete
digestion thereof with a suitable restriction enzyme and by the
subsequent recovery of the relevant fragments. The DNA disclosed
above can be resorted to also as a source of suitable fragments.
The techniques disclosed in PCT application for the isolation of
the fragments which can then be included in suitable plasmids are
applicable here too. Of course, other methods can be used, some of
which have been exemplified in European Application No. 178,978,
filed Sep. 17, 1985. Reference is for instance made to the
following methods:
a) DNA can be transfected into mammalian cells with appropriate
selection markers by a variety of techniques, such as calcium
phosphate precipitation, polyethylene glycol, protoplast-fusion,
etc.
b) DNA fragments corresponding to genes can be cloned into
expression vectors for E. coli, yeast- or mammalian cells and the
resultant proteins purified.
c) The provival DNA can be "shot-gunned" (fragmented) into
procaryotic expression vectors to generate fusion polypeptides.
Recombinants, producing antigenically competent fusion proteins,
can be identified by simply screening the recombinants with
antibodies against LAV antigens.
The invention further refers to DNA recombinants, particularly
modified vectors, including any of the preceding DNA sequences
adapted to transform corresponding microorganisms or cells,
particularly eucaryotic cells such as yeasts, for instance
Saccharomvces cerevisiae, or higher eucaryotic cells, particularly
cells of mammals, and to permit expression of said DNA sequences in
the corresponding microorganisms or cells. General methods of that
type have been recalled in the abovesaid PCT international patent
aplication PCT/EP 85/00548, filed Oct. 18, 1985.
More particularly the invention relates to such modified DNA
recombinant vectors modified by the abovesaid DNA sequences and
which are capable of transforming higher eucaryotic cells
particularly mammalian cells. Preferably, any of the abovesaid
sequences are placed under the direct control of a promoter
contained in said vectors and recognized by the polymerases of said
cells, such that the first nucleotide codons expressed correspond
to the first triplets of the above-defined DNA sequences.
Accordingly, this invention also relates to the corresponding DNA
fragments which can be obtained from the genome of LAV.sub.ELI or
its cDNA by any appropriate method. For instance, such a method
comprises cleaving said LAV.sub.ELI genome or its cDNA by
restriction enzymes preferably at the level of restriction sites
surrounding said fragments and close to the opposite extremities
respectively thereof, recovering and identifying the fragments
sought according to sizes, if need be checking their restriction
maps or nucleotide sequences (or by reaction with monoclonal
antibodies specifically directed against epitopes carried by the
polypeptides encoded by said DNA fragments), and further if need
be, trimming the extremities of the fragment, for instance by an
exonucleolytic enzyme such as Bal31, for the purpose of controlling
the desired nucleotid-sequences of the extremities of said DNA
fragments or, conversely, repairing said extremities with Klenow
enzyme and possibly ligating the latter to synthetic polynucleotide
fragments designed to permit the reconstitution of the nucleotide
extremities of said fragments. Those fragments may then be inserted
in any of said vectors for causing the expression of the
corresponding polypeptide by the cell transformed therewith. The
corresponding polypeptide can then be recovered from the
transformed cells, if need be after lysis thereof, and purified by
methods such as electrophoresis. Needless to say, all conventional
methods for performing these operations can be resorted to.
The invention also relates more specifically to cloned probes which
can be made starting from any DNA fragment according to this
invention, thus to recombinant DNAs containing such fragments,
particularly any plasmids amplifiable in procaryotic or eucaryotic
cells and carrying said fragments. Using the cloned DNA fragments
as a molecular hybridization probe--either by labelling with
radionucleotides or with fluorescent reagents--LAV virion RNA may
be detected directly in the blood, body fluids and blood products
(e.g. of the antihemophylic factors such as Factor VIII
concentrates) and vaccines (e.g., hepatitis B vaccine). It has
already been shown that whole virus can be detected in culture
supernatants of LAV producing cells. A suitable method for
achieving that detection comprises immobilizing virus on a support
(e.g., a nitrocellulose filter), disrupting the virion and
hybridizing with labelled (radiolabelled or "cold" fluorescent- or
enzyme-labelled) probes. Such an approach has already been
developed for Hepatitis B virus in peripheral blood [SCOTTO J. et
al. Hepatology (1983), 3, 379-384].
Probes according to the invention can also be used for rapid
screening of genomic DNA derived from the tissue of patients with
LAV related symptoms, to see if the proviral DNA or RNA present in
host tissue and other tissues can be related to that of
LAV.sub.ELI.
A method which can be used for such screening comprises the
following steps: extraction of DNA from tissue, restriction enzyme
cleavage of said DNA, electrophoresis of the fragments and Southern
blotting of genomic DNA from tissues, subsequent hybridization with
labelled cloned LAV proviral DNA. Hybridization in situ can also be
used.
Lymphatic fluids and tissues and other non-lymphatic tissues of
humans, primates and other mammalian species can also be screened
to see if other evolutionnary related retrovirus exist. The methods
referred to hereinabove can be used, although hybridzation and
washings would be done under non-stringent conditions.
The DNAs or DNA fragments according to the invention can be used
also for achieving the expression of viral antigens of LAV.sub.ELI
for diagnostic purposes.
The invention relates generally to the polypeptides themselves,
whether synthesized chemically, isolated from viral preparations or
expressed by the different DNAs of the invention, particularly by
the ORFs or fragments thereof in appropriate hosts, particularly
procaryotic or eucaryotic hosts, after transformation thereof with
a suitable vector previously modified by the corresponding
DNAs.
More generally, the invention also relates to any of the
polypeptide fragments (or molecules, particularly glycoproteins
having the same polypeptidic backbone as the polypeptides mentioned
hereinabove) bearing an epitope characteristic of a protein or
glycoprotein of LAV which polypeptide or molecule then has
N-terminal and C-terminal extremities respectively either free or,
independently from each other, covalently bonded to amino acids
other than those which are normally associated with them in the
larger polypeptides or glycoproteins of the LAV virus, which last
mentioned amino acids are then free or belong to another
polypeptidic sequence. Particularly, the invention relates to
hybrid polypeptides containing any of the
epitopebearing-polypeptides which have been defined more
specifically hereinabove, recombined with other polypeptides
fragments normally foreign to the LAV proteins, having sizes
sufficient to provide for an increased immunogenicity of the
epitope-bearing-polypeptide yet, said foreign polypeptide fragments
either being immunogenically inert or not interfering with the
immunogenic properties of the epitope-bearing-polypeptide.
Such hybrid polypeptides, which may contain from 5 up to 150, even
250 amino acids, usually consist of the expression products of a
vector which contained ab initio a nucleic acid sequence
expressible under the control of a suitable promoter or replicon in
a suitable host, which nucleic acid sequence had however beforehand
been modified by insertion therein of a DNA sequence encoding said
epitope-bearing-polypeptide.
Said epitope-bearing-polypeptides, particularly those whose
N-terminal and C-terminal amino acids are free, are also accessible
by chemical synthesis according to technics well known in the
chemistry of proteins.
The synthesis of peptides in homogeneous solution and in solid
phase is well known. In this respect, recourse may be had to the
method of synthesis in homogeneous solution described by Houbenweyl
in the work entitled "Methoden der Organischen Chemie" (Methods of
Organic Chemistry) edited by E. WUNSCH., vol. 15-I and II, THIEME,
Stuttgart 1974. This method of synthesis consists of successively
condensing either the successive amino acids in twos, in the
appropriate order or successive peptide fragments previously
available or formed and containing already several amino-acyl
residues in the appropriate order respectively. Except for the
carboxyl and aminogroups which will be engaged in the formation of
the peptide bonds, care must be taken to protect beforehand all
other reactive groups borne by these amino-acyl groups or
fragments. However, prior to the formation of the peptide bonds,
the carboxyl groups are advantageously activated, according to
methods well known in the synthesis of peptides. Alternatively,
recourse may be had to coupling reactions bringing into play
conventional coupling reagents, for instance of the carbodiimide
type, such as 1-ethyl-3-(3-dimethyl-amino-propyl)-carbodiimide.
When the amino acid group used carries an additional amine group
(e.g., lysine) or another acid function (e.g., glutamic acid),
these groups may be protected by carbobenzoxy or t-butyloxycarbonyl
groups, as regards the amine groups, or by t-butylester groups, as
regards the carboxylic groups. Similar procedures are available for
the protection of other reactive groups for example, an -SH group
(e.g., in cysteine) can be protected by an acetamidomethyl or
paramethoxybenzyl group.
In the case of a progressive synthesis, amino acid by amino acid,
the synthesis starts preferably with the condensation of the
C-terminal amino acid with the amino acid which corresponds to the
neighboring aminoacyl group in the desired sequence and so on, step
by step, up to the N-terminal amino acid. Another preferred
technique which can be used is that described by R. D. Merrifield
in "Solid Phase Peptide Synthesis" [J. Am. Chem. Soc., 45,
2149-2154]. In accordance with the Merrifield process, the first
C-terminal amino acid of the chain is fixed to a suitable porous
polymeric resin, by means of its carboxylic group, the amino group
of the amino acid then being protected, for example by a
t-butyloxycarbonyl group. When the first C-terminal amino acid is
thus fixed to the resin, the protective group of the amine group is
removed by washing the resin with an acid, i.e., trifluoroacetic
acid, when the protective group of the amine group is a
t-butyloxycarbonyl group. Then, the carboxylic group of the second
amino acid, which is to provide the second amino-acyl group of the
desired peptidic sequence, is coupled to the deprotected amine
group of the C-terminal amino acid fixed to the resin. Preferably,
the carboxyl group of this second amino acid has been activated,
for example by dicyclohexyl-carbodiimide, while its amine group has
been protected, for example by a t-butyloxycarbonyl group. The
first part of the desired peptide chain, which comprises the first
two amino acids, is thus obtained. As previously, the amine group
is then deprotected, and one can further proceed with the fixing of
the next amino-acyl group and so forth until the whole peptide
sought is obtained. The protective groups of the different side
groups, if any, of the peptide chain so formed can then be removed.
The peptide sought can then be detached from the resin, for example
by means of hydrofluoric acid, and finally recovered in pure form
from the acid solution according to conventional procedures.
As regards the peptide sequences of smallest size bearing an
epitope or immunogenic determinant, and more particularly those
which are readily accessible by chemical synthesis, it may be
required, in order to increase their in vivo immunogenic character,
to couple or "conjugate" them covalently to a physiologically
acceptable and non-toxic carrier molecule. By way of examples of
carrier molecules or macromolecular supports which can be used for
making the conjugates according to the invention can be mentioned
natural proteins, such as tetanic toxoid, ovalbumin,
serum-albumins, hemocyanins, etc. Synthetic macromolecular
carriers, for example polysines or
poly(D-L-alanine)-poly(L-lysine)s, can be used too. Other types of
macromolecular carriers that can be used, which generally have
molecular weights higher than 20,000, are known from the
literature. The conjugates can be synthesized by known processes
such as are described by Frantz and Robertson in "Infect and
Immunity", 33, 193-198 (1981) and by P. E. Kauffman in "Applied and
Environmental Microbiology", October 1981 Vol. 42, No. 4, pp.
611-614. For instance, the following coupling agents can be used:
glutaric aldehyde, ethyl chloroformate, water-soluble carbodiimides
such as(N-ethyl-N'(3-dimethylamino-propyl) carbodiimide, HC1),
diisocyanates, bis-diazobenzidine, di- and trichloro-s-triazines,
cyanogen bromides and benzaquinone, as well as the coupling agents
mentioned in "Scand. J. Immunol.", 1978, vol. 8, pp. 7-23
(Avrameas, Ternynck, Guesdon).
Any coupling process can be used for bonding one or several
reactive groups of the peptide, on the one hand, and one or several
reactive groups of the carrier, on the other hand. Again coupling
is advantageously achieved between carboxyl and amine groups
carried by the peptide and the carrier or vice-versa in the
presence of a coupling agent of the type used in protein synthesis,
e.g., 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide,
N-hydroxybenzotriazole, etc. Coupling between amine groups
respectively borne by the peptide and the carrier can also be made
with glutaraldehyde, for instance, according to the method
described by BOQUET, P. et al. (1982) Molec. Immunol., 19,
1441-1549, when the carrier is hemocyanin.
The immunogenicity of epitope-bearing-peptides can also be
reinforced by oligomerisation thereof, for example in the presence
of glutaraldehyde or any other suitable coupling agent. In
particular, the invention relates to the water soluble immunogenic
oligomers thus obtained, comprising particularly from 2 to 10
monomer units.
The glycoproteins, proteins and other polypeptides (generally
designated hereinafter as "antigens" of this invention) whether
obtained by methods, such as are disclosed in the earlier patent
applications referred to above, in a purified state from LAVELI
virus preparations or--as concerns more particularly the
peptides--by chemical synthesis, are useful in processes for the
detection of the presence of anti-LAV antibodies in biological
media, particularly biological fluids such as sera from man or
animal, particularly with a view of possibly diagnosing LAS or
AIDS.
Particularly the invention relates to an in vitro process of
diagnosis making use of an envelope glycoprotein or of a
polypeptide bearing an epitope of this glycoprotein of LAV.sub.ELI
for the detection of anti-LAV antibodies in the serums of persons
who carry them. Other polypeptides--particular those carrying an
epitope of a core protein--an be used too.
A preferred embodiment of the process of the invention
comprises:
depositing a predetermined amount of one or several of said
antigens in the cups of a titration microplate;
introducing increasing dilutions of the biological fluid, to be
diagnosed (e.g., blood serum, spinal fluid, lymphatic fluid, and
cephalo-rachidian fluid), into these cups;
incubating the microplate;
washing carefully the microplate with an appropriate buffer;
adding into the cups specific labelled antibodies directed against
blood immunoglobulins and
detecting the antigen-antibody-complex formed, which is then
indicative of the presence of LAV antibodies in the biological
fluid.
Advantageously the labelling of the anti-immunoglobulin antibodies
is achieved by an enzyme selected from among those which are
capable of hydrolysing a substrate, which substrate undergoes a
modification of its radiation-absorption, at least within a
predetermined band of wavelenghts. The detection of the substrate,
preferably comparatively with respect to a control, then provides a
measurement of the potential risks, or of the effective presence,
of the disease.
Thus, preferred methods of immuno-enzymatic and also
immunofluorescent detections, in particular according to the ELISA
technique, are provided. Titrations may be determinations by
immunofluorescence or direct or indirect immuno-enzymatic
determinations. Quantitative titrations of antibodies on the serums
studied can be made.
The invention also relates to the diagnostic kits themselves for
the in vitro detection of antibodies against the LAV virus, which
kits comprise any of the polypeptides identified herein and all the
biological and chemical reagents, as well as equipment, necessary
for peforming diagnostic assays. Preferred kits comprise all
reagents required for carrying out ELISA assays. Thus preferred
kits will include, in addition to any of said polypeptides,
suitable buffers and anti-human immunoglobulins, which anti-human
immunoglobulins are labelled either by an immunofluorescent
molecule or by an enzyme. In the last instance, preferred kits also
comprise a substrate hydrolysable by the enzyme and providing a
signal, particularly modified absorption of a radiation, at least
in a determined wavelength, which signal is then indicative of the
presence of antibody in the biological fluid to be assayed with
said kit.
It can of course be of advantage to use several proteins or
polypeptides not only of LAV.sub.ELI but also of LAV.sub.MAL
together with homologous proteins or polypeptides of earlier
described viruses, such as LAV.sub.BRU, HTLV-3, ARV 2, etc.
The invention also relates to vaccine compositions whose active
principle is to be constituted by any of the antigens, i.e., the
hereinabove disclosed polypeptides of LAV.sub.ELI particularly the
purified gp110 or immunogenic fragments thereof, fusion
polypeptides or oligopeptides in association with a suitable
pharmaceutically or physiologically acceptable carrier. A first
type of preferred active principle is the gp110 immunogen of said
immunogens. Other preferred active principles to be considered in
that fields consist of the peptides containing less than 250 amino
acid units, preferably less than 150, particularly from 5 to 150
amino acid residues, as deducible for the complete genome of
LAV.sub.ELI and even more preferably those peptides which contain
one or more groups selected from Asn-X-Thr and Asn-X-Ser as defined
above. Preferred peptides for use in the production of vaccinating
principles are peptides (a) to (f) as defined above. By way of
example, there may be mentioned that suitable dosages of the
vaccine compositions are those which are effective to elicit
antibodies in vivo, in the host, particularly a human host.
Suitable doses range from 10 to 500 micrograms of polypeptide,
protein or glycoprotein per kg, for instance 50 to 100 micrograms
per kg.
The different peptides according to this invention can also be used
themselves for the production of antibodies, preferably monoclonal
antibodies specific for the respective different peptides. For the
production of hybridomas secreting said monoclonal antibodies,
conventional production and screening methods can be used. These
monoclonal antibodies, which themselves are part of the invention,
provide very useful tools for the identification and even
determination of relative proportions of the different polypeptides
or proteins in biological samples, particularly human samples
containing LAV or related viruses.
The invention further relates to the hosts (procaryotic or
eucaryotic cells) which are transformed by the above mentioned
recombinants and which are capable of expressing said DNA
fragments.
Finally the invention also concerns vectors for transforming
eucaryotic cells of human origin, particularly lymphocytes, the
polymerase of which are capable of recognizing the LTRs of LAV.
Particularly said vectors are characterized by the presence of a
LAV LTR therein, said LTR being then active as a promoter enabling
the efficient transcription and translation in a suitable host of a
DNA insert coding for a determined protein placed under its
controls.
Needless to say, the invention extends to all variants of genomes
and corresponding DNA fragments (ORFs) having substantially
equivalent properties, all of said genomes belonging to
retroviruses which can be considered as equivalents of LAV.sub.ELI.
It must be understood that the claims which follow are also
intended to cover all equivalents of the products (glycoproteins,
polypeptides, DNAs, etc.) whereby an equivalent is a product, e.g.,
a polypeptide, which may distinguish from a product defined in any
of said claims, say through one or several amino acids, while still
having substantially the same immunological or immunogenic
properties. A similar rule of equivalency shall apply to the DNAs,
it being understood that the rule of equivalency will then be tied
to the rule of equivalency pertaining to the polypeptides which
they encode.
It will also be understood that all the literature referred to
hereinbefore and hereinafter and all patent applications and
patents not specifically identified herein but which form
counterparts of those specifically designated herein, must be
considered as incorporated herein by reference.
It should further be mentioned that the invention further relates
to immunogenic compositions that contain preferably one or more of
the polypeptides, which are specifically identified above and which
have the amino acid sequences of LAV.sub.ELI that have been
identified, or peptidic sequences corresponding to previously
defined LAV proteins. In this respect, the invention relates more
particularly to the particular polypeptides which have the
sequences corresponding more specifically to the LAV.sub.BRU
sequences which have been referred to earlier, i.e., the sequences
extending between the following first and last amino acids, of the
LAV.sub.BRU proteins themselves, i.e., the polypeptides having
sequences contained in the LAV.sub.BRU OMP or LAV.sub.BRU TMP or
sequences extending over both, particularly those extending from
between the following positions of the amino acids included in the
env open reading frame of the LAV.sub.BRU genome,
1-530
34-530
and more preferably
531-877, particularly 680-700,
37-130
211-289
488-530
490-620.
These different sequences can be used for any of the above defined
purposes and in any of the compositions which have been
disclosed.
Finally the invention also relates to the different antibodies
which can be formed specifically against the different peptides
which have been disclosed herein, particularly to the monoclonal
antibodies which recognize them specifically. The corresponding
hybridomas which can be formed starting from spleen cells
previously immunized with such peptides which are fused with
appropriate myeloma cells and selected according to standard
procedures also form part of the invention.
Phage .lambda. clone E-H12 derived from LAV.sub.ELI infected cells
has been deposited at the CNCM under No. I-550 on May 9, 1986.
Phage clone M-H11 derived from LAV.sub.MAL infected cells has been
deposited at the CNCM under No. I-551 on May 9, 1986.
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